The proposed research plan represents a series of multidisciplinary investigations which will characterize the motor-related output from limbic forebrain and brainstem regions to the back axial muscles during the performance of a hormone-dependent behavior in chronic preparations. The lordosis reflex of the rat will serve as the model behavior. Neural stimulation, endocrine dose-response, and electromyographic methodologies are employed in order to study limbic and hormonal influences on the electromyographic records of lumbar musculature. Temporal comparisons will be made between 1) the EMG profiles of the motor output with and without neural stimulation, 2) postural data obtained from a length gauge fastened to the vertebral column, and 3) the onset and duration of the somatosensory stimulation which elicits motor output. These comparisons will provide information concerning 1) the influences of limbic forebrain and brainstem stimulation on spinal motor mechanisms which effect the behavioral output, 2) a correlation of muscle activity with the characteristic vertebral dorsiflexion of lordosis, 3) duration of muscle activity during the behavior, 4) the onset latencies of activity of the muscles involved with respect to the onset of cutaneous stimulation, and 5) the effects of estrogen and progesterone administration on the EMG response. Acute studies of the influences of limbic forebrain regions on the axial musculature will complement existing data on the influences from the pontomedullary reticular formation. The participation of limbic structures in lordosis behavior, the endocrine dependence of the behavior, the involvement of postural muscles which have been implicated in tension, stress, and lower lumbar back pain, the quantifiability of the data base, and the proven methodology all contribute to the justification that this systems serves as a viable model of emotional behavior. The proposed research plan not only serves as a logical next step in the analysis of this sterotyped behavior, it also represents the initial phase of this investigator's goal study the limbic control of emotional responses.